1. Field of the Invention
The present invention relates to an electric wire connection structure in which a first member and a second member clamping an electric wire and a terminal therebetween are welded to each other by application thereto of ultrasonic vibration.
2. Description of Relevant Art
In Japanese Patent Publication No. 7-70345 there is described a method of welding to each other a first member and a second member clamping an electric wire and a terminal therebetween by application thereto of ultrasonic vibration.
FIGS. 1A and 1B show a connector which is manufactured by this conventional method and in which a first member and a second member each made of resin oppose each other.
In an upper surface of the first member there is formed a groove portion 3 in the longitudinal direction thereof and small concave portions 4 are formed at suitable intervals in the longitudinal direction of the groove portion 3. In the groove portion 3 of the first member 1 there is inserted in the longitudinal direction thereof a terminal 5 on which a covered electric wire 6 is placed. The covered electric wire 6 is placed on the terminal 5 in a state where a number of core wires are covered by an insulating covering.
On an underside of the second member 2 there is formed a protruding portion 7 which is to be fitted into the groove portion 3 of the first member 1 and there are formed small convex portions 8 which are to be fitted into the concave portions 4 of the groove portion 3.
When assembling this structure, the protruding portion 7 of the second member 2 is fitted into the groove portion 3 of the first member 1 in a state where the terminal 5 and the covered electric wire 6 are inserted into the groove portion 3, after which the terminal 5 and the covered electric wire 6 are pressed by the second member 2 and the first member 1. At this time, the terminal 5 and the covered electric wire 6 are partially bent at the portions wherein the concave portions 4 and the convex portions 8 are interfitted with each other, to thereby prevent draw-off of the terminal 5 and the covered electric wire 6.
And, ultrasonic vibration is applied from a horn (not shown) with the first member 1 and the second member 2 being clamped thereby. Due to the heat generated by application of ultrasonic vibration, an insulating covering of the covered electric wire 6 is molten and removed with the result that a core wire of the covered electric wire 6 and the terminal 5 are contacted with each other and brought into electric conduction therebetween. Simultaneously with this electric conduction, due to the heat resulting from the application of ultrasonic vibration the first member 1 and the second member 2 are welded to and integrated with each other. Thus, there can be manufactured a connector having the terminal 5 and electric wire accommodated therewithin.
FIG. 2 shows a conventional structure for manufacturing a multi-polar connector. In this connector, a plurality of groove portions 3 are formed in the first member 1 and a plurality of protruding portions 2 which oppose these groove portions 3 are formed in the second member 2. And, a terminal is accommodated in each groove 3, a covered electric wire is placed on the terminal, and thereafter the resulting laminate is pressed by the first member 1 and the second member 2. Then, ultrasonic vibration is applied thereto in an identical way as mentioned above to thereby provide a connector.
In the structure of FIG. 2 also, as in the case of FIGS. 1A and 1B, small concave portions are formed in the groove 3 of the first member 1 and small convex portions are formed on the protruding portion 7 of the second member 2.
FIG. 3 shows a state where the terminal 5 and the covered electric wire 6 are clamped between the first member 1 and second member 2 having the above-described structure. By being pressed by the protruding portion of the second member 2, the terminal 5 and the covered electric wire 6 are superposed one over the other and are bent at their portions corresponding to the convex portions and the concave portions 4. Reference symbols 5a and 6a designate bent portions thereof. By forming the bent portions 5a and 6a in the terminal 5 and covered electric wire 6 as mentioned above, it is possible to prevent these members from being drawn off.
However, in the conventional structure, there occurs the phenomenon that the terminal 5 is buried when ultrasonic vibration is applied. FIG. 4 illustrates this phenomenon and FIG. 5 is an enlarged cross section of a portion B of FIG. 4.
Due to the heat generated by application of ultrasonic vibration, the first member 1 and the second member 2 are softened. When in this state the second member 2 is pressed against the first member 1, this first member 1 with which the terminal 5 contacts is somewhat recessed or depressed by being pressed. For this reason, an end portion of the terminal 5 is embedded or buried in the first member 1 and thus is lowered in level from a horizontal line H shown in FIG. 5, with the result that the position of the terminal 5 as a whole is lowered more than the designed position. This embedment prominently occurs particularly at the groove portion of the first member locally pressed by the protruding portion 7 of the second member.
When the position of the terminal 5 becomes lowered from the designed position due to such embedment, interfitting or contacting of the terminal 5 with a terminal of a mating connector to which the terminal 5 is connected cannot be effected, raising the problem that electrical connection between the connectors becomes impossible.